disable_sigint() throws SIGINT away rather than defers it.

[alicedb2]

I'm running a MCMC algorithm with the following basic structure. I'm using Julia 1.7.2 on MacOS.

try
    while true
        disable_sigint() do
            for i in 1:5
                # Slow, critical, interrupt unsafe code
                sleep(1)
                print(".")
            end
        end
        
        # Fast, interrupt safe code
        println("\nnow it is safe to interrupt immediately")
    end
catch InterruptException
    println("interrupt catched")
end

Despite pressing [I],[I] or clicking "Interrupt Kernel" in the kernel menu this code never interrupts. Given the next scenario I think it would work if I had superhuman reflexes and were able to hit [I], [I] exactly during the few microseconds of fast code outside the do-block.

Alternatively, if instead of wrapping the whole thing into a while-true I put a slow block of code outside the disable_sigint() block like so

try
    disable_sigint() do
        for i in 1:5
            sleep(1)
            print(".")
        end
    end

    # Slow, interrupt safe code
    println("\nnow it is safe to interrupt immediately")

    while true
        sleep(1)
        print("*")
    end
catch InterruptException
    println("interrupt catched")
end

then I can interrupt the code by hitting [I], [I] when inside the slow while-true block. If I hit [I], [I] while inside the `do-block' nothing happens and SIGINT is apparently thrown away and not deferred to the slow part.

I tested the exact same code in both cases in the base REPL and it works as expected. When hitting Ctrl+C the SIGINT is queued and deferred until just outside the do-block and the InterruptException is caught.